The invention concerns a system for mounting and attaching prismatic rooted vanes in a turbine and compressor rotor, and a procedure for mounting said blades in the rotor disc. 2. Description of the Prior Art
The use of prismatic rooted blades in turbine and compressor rotors allows simplification of the locking systems, since attachment of the blades is achieved by a single system placed last between two neighboring blades.
A disc intended to be filled with prismatic rooted blades has in its rim a circumferential groove into which the roots are introduced and then held.
Such a system is described for example in French Pat. No. 1,112,826. The groove provided in the disc has, from the outside towards the center of the disc, two peripheral flanges separated by a distance equal to the length of the platform and between which the platform is housed when the blade is in place, a narrow part corresponding to the length of the shank, and finally a part wider than the length of the blade root and higher than the distance separating the lower part of the blade root from the upper part of the platform. An insertion opening is provided in the groove and is obtained by removal of the narrow part over a length equal to the width of the platform.
The prismation rooted blade cooperating with the groove has a platform surmounting and projecting beyond a parallelepipedal shank and a root projecting beyond the ends of the stilt.
The mounting process consists of introducing the blade into the groove along the smallest dimension of the root, then bringing the blade into the opening and, after subjecting it to a 90.degree. rotation, turning it towards the outside so as to bring the root to rest against the upper part of the opening. The blade is then slid circumferentially, with the platform being housed between the peripheral flanges of the groove. The same operation is repeated for each blade.
The last blade or blocking blade has at least one edge of its platform removed and replaced with a spline attached in slits made in the shank. The blocking blade is brought up between the blades placed on either side of the opening and is held between them by the turned-down spline.
This type of system, generally utilized for prismatic rooted blades, has the drawback of weakening the disc in the area of the insertion opening and results in poor fatigue resistance.